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Date: Fri, 7 Jan 2011 17:03:48 -0500 (EST)
From: "Namit Jain (JIRA)" <jira@apache.org>
To: hive-dev@hadoop.apache.org
Subject: [jira] Commented: (HIVE-1900) a mapper should be able to span
 multiple partitions
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    [ https://issues.apache.org/jira/browse/HIVE-1900?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12978987#action_12978987 ] 

Namit Jain commented on HIVE-1900:
----------------------------------

1. Why should it be any different than sort-merge join ?
    ExecMapper needs to keep track of the current file, and then change the partitioning columns whenever the file changes
2. Why should it matter ?
3. Why should it matter ?

> a mapper should be able to span multiple partitions
> ---------------------------------------------------
>
>                 Key: HIVE-1900
>                 URL: https://issues.apache.org/jira/browse/HIVE-1900
>             Project: Hive
>          Issue Type: Improvement
>          Components: Query Processor
>            Reporter: Namit Jain
>            Assignee: He Yongqiang
>
> Currently, a  mapper only spans a single partition which creates a problem in the presence of many
> small partitions (which is becoming a common usecase in facebook).
> If the plan is the same, a mapper should be able to span files across multiple partitions

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